返回值

Returns the value encoded in input in appropriate
PHP type 或者在失败时返回 FALSE. If pos is -1 an
array will be returned with one entry for each document found
in the stream.

注释

Warning

Processing untrusted user input with yaml_parse_file()
is dangerous if the use of unserialize() is enabled for
nodes using the !php/object tag. This behavior can be
disabled by using the yaml.decode_php ini setting.

This is entirely dependent on type detection - as far as I can find there is no way to force a type and for instance when you have a very long integer as a value - in my case 1313035348823 it gets limited to 2147483647 - PHP's max integer.